(Updated) The case of the Miami “zombie” — a horrific attack last Saturday in which a naked man chewed most of the flesh off another man’s face before being shot and killed by police — is now being attributed to various devilish drugs.

Some police officers say he overdosed on some kind of new, highly potent LSD; others have blamed cocaine. A police union representative told MSNBC.com: “Whenever we see that a person has taken all of his clothes off and has become violent, it’s indicative of this excited delirium that’s caused by overdose of drugs. What’s happening is inside their body, their organs are burning up alive.”

But without a toxicology report, all of this is little more than speculation. Police officers are also notoriously misinformed about how drugs actually affect behavior. Just consider the wide variety of credulous urban legends spread by cops about drugs.

From potentially deadly acid-laced temporary tattoos that drug dealers were supposedly handing out to elementary school children to “musical drugs” that use specific rhythms to get you high to “jenkem,” intoxicating gas produced by raw sewage , there seems to be no drug-fueled tall tale that police officers won’t publicize. (I won’t deny for a second that the rumor mill is enabled by reporters who seem to drop any remnant of critical thinking and skepticism the moment drugs are mentioned.)

So, what’s the truth about the role of drugs in bizarre, violent behavior such as that of the Miami man? The first thing to understand is that most drug-related violence has nothing to do with any pharmacological effects of drugs on the brain, and everything to do with a drug’s legal status.

For example, a study published in the late 1990s looked at murders in New York City about 10 years earlier, in 1988 — one of the city’s most violent years, near the peak of the so-called crack epidemic. That year, three-quarters of all people arrested in the city tested positive for cocaine.

However, only 7.5% of the 414 killings that occurred between March and October 1988 involved people who had taken drugs, mostly alcohol; five cases, or 1%, involved people who had smoked crack. About 2% involved people who committed their crimes to get drug money. And fully 40% of the slayings involved drug trade disputes — of the type that has not been seen with alcohol since Prohibition. Overall, nearly half of all homicides had no connection to drugs whatsoever.

Moreover, a study published in January by the Centers for Disease Control and Prevention that examined gang killings showed that in most cities, fewer than 20% of these murders involve the use or sales of drugs.

To look at the question from another angle, consider the number of people who have taken drugs that are purported to cause violence. More than 37 million Americans report trying cocaine at least once; 9 million have admitted smoking crack; LSD has been taken by some 23 million U.S citizens. Imagine the mayhem if each of these users turned violent.

Further, synthetic marijuana — which is sold as “K2” or “Spice” and has also been blamed recently for violent crimes — has been tried by 11% of American high school seniors. There are no figures for another “legal high” known as bath salts, which contain amphetamine-like compounds and which an emergency room doctor blamed for the Miami attack.

Basically, if drugs were a simple cause of violence, we’d be in far more trouble than we are now, with a crime rate many times what it actually is. Indeed, despite the rise of the new legal highs, rates of violent crime have generally adhered to a decades-long decline.

This is not to say that certain drugs cannot cause bizarre or extreme reactions in certain vulnerable people in certain situations. At high doses, both cocaine and amphetamine can induce paranoid and psychotic behavior, for example. There is some indication that this is true of some legal highs as well; little is known about them because they were not tested in humans before being marketed.

But stimulants of any type rarely lead to violence in people who don’t have a prior history of violent behavior. Typically, drugs enhance or disinhibit pre-existing tendencies, rather than provoking entirely new behavior. And drugs are far from the only reason that a person might strip naked and become violent, as the Miami man did.

[Update 6:30 p.m.:] Indeed, the best predictor of violent behavior is a previous history of violent behavior, which we now know that the Miami man had. He was apparently the first person ever to be tasered by North Miami Beach police. Why? He had beaten and was threatening to kill his mother.

Also, while overdoses of stimulants do overheat the body, they certainly don’t, as the Miami police representative suggested, “burn organs alive.” Blaming LSD for violent behavior is even further off base. No research has associated LSD or related psychedelic drugs with violence, and higher potency isn’t likely to change that.

When taken by mentally ill people, however, drugs can dramatically increase the risk of violence. A 2009 review of the research found that while having schizophrenia itself may raise a man’s risk of violent behavior by two to four times, drug misuse may multiply that risk by a factor of 12.

By itself, schizophrenia — with or without substance misuse — increases a person’s chance of committing homicide by a factor of nearly 20. And yet, in the press, drugs continue to get the primary blame for such crimes. Yes, drugs do exacerbate the risks associated with mental illness like schizophrenia, but the main reason we’re so quick to pin it all on drugs is a quirk of human psychology that skews our view of other people’s behavior.

It’s called the clinician’s error, but it could just as easily be called the “police officer’s error” or the “journalist’s error.” The basic tenet is that people in medicine, law enforcement and media tend to see and focus on extremes.

Drug-treatment professionals don’t often interact with the roughly 85% of users who don’t become addicts; cops don’t spend much time with people whose drug use doesn’t lead to misbehavior; and journalists don’t generally focus on the uneventful. Therefore, their views on drugs are distorted.

Imagine if you grew up in a place where no one drank alcohol, then you went to work in an E.R. where your only exposure to the effects of booze was overdosed college kids, victims of drunk-driving accidents and patients with severe liver disease. You probably would view all drinking as extremely risky because you’d have no exposure to the majority of people who drink moderately and never wind up in the hospital.

Police get a similarly one-sided view of substance use, and as a result, they’re often willing to believe the most extreme statements about drugs. Police training doesn’t include intensive education in pharmacology, addiction treatment or epidemiology. What police are taught, of course, is designed to make them effective soldiers in the nation’s drug war. Journalists, who often rely on the police for drug information, then wind up conveying misinformation.

This is not to pick on the police. It’s merely to note that providing accurate information about drugs is not one of their strong points, and there’s no reason that it should be. If we want to understand what really went wrong in that Miami incident, we need to find out the real facts and then explore the relevant research, not regurgitate drug hysteria.

Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.